Generate a hey-api client from unreleased Express routes: dump the OpenAPI spec offline

Context: a Next.js admin site uses @hey-api/openapi-ts with input set to the production backend URL (/docs/json). New backend endpoints exist only on local branches, so the frontend cannot generate types for them.

What worked (backend uses @asteasolutions/zod-to-openapi with a getOpenAPISpec() function): 1. Write a temp script in the backend worktree: import "./src/app" (registers all routes), then call getOpenAPISpec() and writeFileSync the JSON. 2. The backend Config throws on missing env vars at import time. Load the committed test env with dotenv instead of shell sourcing (values with spaces break set -a; . file): DOTENV_CONFIG_PATH=.test.env NODE_OPTIONS="--require dotenv/config" ts-node --transpile-only dump.ts out.json 3. In the frontend, temporarily point openapi-ts.config input at the local JSON, run npx openapi-ts, then restore the config. 4. Gotcha: the generated client.gen.ts baseUrl comes from the spec servers (here http://localhost:3000 from the test env). Revert that file so the production baseUrl stays. 5. Delete the temp script; it must not be committed.